Support fixture



E. H. TUBBS SUPPORT FIXTURE Juiy 8, 1958 Filed May 1'7, 1957 a y 2 th wn .mt @Wfi VI A United States Patent SUPPORT FIXTURE.

Elton H. Tubbs, Westfi'eld, N. Y., assignor to General Electric Company,a corporation of New York Application May 17, 1957, Serial No. 659,801

2 Claims. (Cl. 310-240) My invention relates to a support fixture and,more particularly, to a support fiXture for maintaining the tips ofbrush pressure springs of a dynamoelectric machine in a raised positionto facilitate removal of the brushes.

For many years the electrical industry maintenance people have attemptedto retract brush pressure springs with screwdrivers and other unsuitableinstruments. Generally, such operation requires the use of two hands,one to hold the lever tip in a retracted position and the other tomanipulate the brush. With larger machines such as those having 600volt, 1,000 horsepower ratings, this is both hazardous and difiicult.With a locomotive traction motor which is supported on the unsprung axleand subjected to severe vibrations, the spring tension must be suhicientto maintain the brushes in electrical contact with the commutatordespite inherent mechanical shocks.

Experience has led to the use of insulation between the spring lever tipand the brush to prevent current flow within the spring thus preventingtemperature rise thereof above the ambient to eliminate tempering of thesteel of the spring. With the tension required, one of the most commonhazards is the recurring damage caused by the use of improvised holdinginstruments such as sharp steel screwdrivers directly on relatively softinsulation secured to the spring'lever tip. Another hazard is theprobability that the spring lever tip will slip from its retractedposition and because of its momentum will damage the bnlsh'itself or anyintervening material such as the insulation or the operators fingers.The hazard is further increased by the fact that certain of the brushesare placed in a relatively inaccessible position whereby the operator isable to use only one hand at a time to change a brush.

Therefore, an object of my invention is to provide a simple and reliablesupport fixture adapted to maintain prestressed springs in a retractedposition.

In carrying out my invention in one preferred form, I have provided asupport fixture adapted to be securely positioned on the brush holderand provided with rungs suitable to maintain the spring lever tips inthe retracted position.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. My invention, however, as to its organization and methodof operation together with further objects and advantages thereof willbest be understood by reference to the following description taken inconnection with the accompanying drawing, in which:

Fig. 1 shows a top plan view of a brush holder having my inventionsecured thereto;

Fig. 2 shows a side view of the arrangement shown in 'Fig. 1; and

Fig. 3 is an enlarged perspective view of my support fixture.

Referring now to the drawing, in which like numerals refer to similarparts, in Fig. 1, I have shown a brush holder 10 adapted to support aplurality of brushes 11 which engage a commutator 12. The brush holder10 may be fabricated, cast or molded of a rigid material which willsupport the brushes 11 in the apertures 13 substantially perpendicularto the adjacent surface of commutator segments. The apertures 13 arepositioned at a precise electrical point on the commutator 12 10- cateda fixed distance from the support pins 14 which are secured to astationary frame (not shown).

With a relatively large machine, it is the usual practice to providespiral brush springs 16 non-rotatably secured to the brush holder 10with the end portion or spring lever tips 18 extending outwardly toengage the top of a brush 11 to maintain adequate brush contact on thecommutator 12. In order to provide desirable tension at the commutatorsurface, the normal pressure and line of motion of the tips 18 isparallel to the major axis of the brushes 16.

To prevent chattering or vibration of the brushes 11 despite violentvibrations of the dynamoelectric machine itself, it is essential thatthe pressure provided by springs 16 be on the order of several pounds.Also, since the tip 18 must :be relatively rigid, it is made with arelatively large mass. This alone would cause a sufficient momentum,should the spring lever tip 18 be raised and then released to drop onthe top of the brush, to damage the brush and, of course, any softmaterial between'the top of the brush 11 and the tip 18.

It has been found that a current flow inthe spring'16 will tend to heatthe springs, temper them and destroy the desired resilience. Usuallythere is a relatively soft insulation material 20 secured between thetip 18 and the brush 11 to prevent an electrical connectiontherebetween. The material 20 is some type of non-conductive plastic orrubber which effectively prevents any current flow within the brushsprings 16.

Also, if a maintenance man happened to have a knuckle or a finger in theregion of the top of the brush 11, unexpected release of the brush tip18, of course, would bruise it.

According to my invention, the brush lever tip 18, when raised from itsoperating position, is placed on a rung 22 of my support fixture 23. Therung 22 projects outwardly perpendicular to the line of motion of thetip 18 a distance sufiicient to provide suitable support. In order toprevent slipping of the lever tips 18, I prefer to have the supportingsurface of the rung 22 roughened or knurled as shown on Fig. 3.Moreover, I have provided enough space between the rung 22 and anyadjacent structure to allow raising or lowering of the tips 18 withoutinterference. As shown more clearly in Fig. 3, the rungs 22 are securedby a weld or braze to curved support members 24 which are mounted on thebrush holder 10. The support members 24 are specifically designed tomaintain the rungs 22 a suflicient distance above the brush holder 10 tosupport the tip 13 in a position which will not interfer with removal ofthe brushes 11. In order to prevent slipping of the brush supportmembers 24, they are provided with recesses 25 between bifurcationswhich straddle the partitions 26 (Fig. l) of a brush holder 10. Achamfer is provided on the bifurcations to facilitate assembly in thebrush holder 10. This is especially helpful when the brush holder cannot be seen. On the back of the members 24 I have provided a step 27which also rests on the partitions 26.

In the particular brush holder illustrated in Figs. 1 and 2, the springs16 are supported on a transverse rod 28. I have found that it ispreferable to provide a support fixture 23 that will not tilt when it isengaged by only one of the tips 18 at either end. In order to preventsuch tilting, I have provided the curved support members 24 with a 3latching means shown as the extensions 30 which pass under and engagethe under side of the rod 28.

In addition, I have connected the two curved support members 24 by arigid brace or cross member 32, which is securely fastened to each bywelding or brazing to provide a rigid one piece fixture. The crossmember 32 is located behind the tip 13, when in the retracted position,so that it will not interfer therewith.

It is readily apparent from Fig. 2 that my support fixture may be easilypositioned for use by placing the extensions 30 under the rod 28 and thelowering the curved portions 24 until the recesses 25 engage thepartitions 26. I prefer to have the fixture 23 securely fastened when asingle lever spring tip is placed on any one of the rungs 22 (as shownat 18a). In this manner, it will remain in place as long as the operatorwishes to work on the brush holder assembly regardless of the locationwithin the machine of the particular brush holder. In other words, thebrush holder 10 may be located on either side, above or below thecommutator 12.

It should also be noted from Fig. 2 that I have shown a worn brush 11a,and a replacement brush 11b. In Fig. 1, I have shown aperture 13a wherethe brush has been removed prior to replacement. According to myinvention, one or all three of the brush lever spring tips 18 conld bemounted on the rungs 22 at the same time whereby one or all three of thebrushes could be removed in one operation by the maintenance manreaching into the machine with one hand.

While I have illustrated and described particular embodiments of myinvention, other modifications will 'occur to those skilled in the art.For instance, I contemplate that a fixture including the rungs 22 may befabricated as shown or molded as a part of a modified brush holder.Obviously, my fixture is adaptable for supporting any number of springlever tips by providing the proper number of rungs 22 supported onconnected support members 24. Also, if a rod similar to that shown at 28is unavailable, other means than the extensions 30 can be used toprevent tilting of my support fixture. I intended, therefore, to coverby the appended claims all such modifications as fall within the truespirit and scope of my invenion.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A support fixture connectable in a dynamoelectric machine, havingspiral brush springs, for maintaining spring lever tips in a retractedposition comprising, a pair lever tips a distance sufiicient to providea platform suitable to support the spring lever tips in a retractedposition allowing unrestricted access to brushes thereunder, and

a cross membersecured to said members for rigidly connecting themtogether, said support members being provided with latching meansadapted to cooperate with said brush holder for preventing tilting ofsaid support members when one or more of the tips are positioned on'saidrungs.

2. A support fixture, connectable in a dynamoelectric machine havingspiral brush springs mounted on a transverse rocl, for maintainingspring lever tips in a retracted position comprising, a pair of supportmembers attachable to a brush holder. and extending outwardly therefrom,a cross member secured to said support members for rigidly connectingthem together, said support members being provided with a plurality ofrigid latching means adapted to cooperate with the transverse rod forpreventing tilting of the support fixture, and rungs secured to saidsupport members and projecting perpendicular to the line of normalmotion of the lever tips a distance sufficient to provide a platformsuitable to support the spring lever tips in a retracted position, saidrungs being positioned a sufiicient distance from said first holder toallow unrestricted access to brushes thereunder with the tips retracted,said rungs being knurled on said platform to prevent slipping of thetips therefrom, said support members, cross member and rungs beingmaintained in position by the tension of one or more of the spring levertips in a retracted position, and being arranged in a spacedrelationship allowing unrestricted movement of the spring lever tip froma brush below one of said rungs to the retracted position above said onerung.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain Mar. 30, 1955

